Rivet analyses
H1 energy flow in DIS
Experiment: H1 (HERA)
Inspire ID: 503947
Status: VALIDATED
Authors: - Peter Richardson
References: - Eur.Phys.J.C12:595-607,2000 - DOI: 10.1007/s100520000287 - arXiv: hep-ex/9907027
Beams: p+ e+
Beam energies: (820.0, 27.5)GeV
Run details: - $e^+ p$ deep inelastic scattering with $p$ at 820~GeV, $e^+$ at 27.5 GeV \to $\sqrt{s} = 300~\GeV$
Measurements of transverse energy flow for neutral current deep- inelastic scattering events produced in positron-proton collisions at HERA. The kinematic range covers squared momentum transfers $Q^2$ from 3.2 to 2200 GeV$^2$; the Bjorken scaling variable $x$ from $8 \times 10^{-5}$ to 0.11 and the hadronic mass $W$ from 66 to 233 GeV. The transverse energy flow is measured in the hadronic centre of mass frame and is studied as a function of $Q^2$, $x$, $W$ and pseudorapidity. The behaviour of the mean transverse energy in the central pseudorapidity region and an interval corresponding to the photon fragmentation region are analysed as a function of $Q^2$ and $W$. This analysis is useful for exploring the effect of photon PDFs and for tuning models of parton evolution and treatment of fragmentation and the proton remnant in DIS.
Source code:H1_2000_I503947.cc
// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Math/Constants.hh"
#include "Rivet/Projections/DISKinematics.hh"
#include "Rivet/Projections/FinalState.hh"
namespace Rivet {
/// @brief H1 energy flow and charged particle spectra
///
/// @author Peter Richardson
///
/// Based on the HZTOOL analysis HZ99091
class H1_2000_I503947 : public Analysis {
public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(H1_2000_I503947);
/// @name Analysis methods
/// @{
/// Initialise projections and histograms
void init() {
// Projections
const DISLepton dl;
declare(dl, "Lepton");
declare(DISKinematics(), "Kinematics");
declare(dl.remainingFinalState(), "FS");
// Histograms and weight vectors for low Q^2 a
_histETLowQa.resize(17);
for (size_t ix = 0; ix < 17; ++ix) {
book(_histETLowQa[ix], ix + 1, 1, 1);
book(_weightETLowQa[ix], "TMP/ETLowQa" + to_string(ix));
}
// Histograms and weight vectors for high Q^2 a
_histETHighQa.resize(7);
for (size_t ix = 0; ix < 7; ++ix) {
book(_histETHighQa[ix], ix + 18, 1, 1);
book(_weightETHighQa[ix], "TMP/ETHighQa" + to_string(ix));
}
// Histograms and weight vectors for low Q^2 b
_histETLowQb.resize(5);
for (size_t ix = 0; ix < 5; ++ix) {
book(_histETLowQb[ix], ix + 25, 1, 1);
book(_weightETLowQb[ix], "TMP/ETLowQb" + to_string(ix));
}
// Histograms and weight vectors for high Q^2 b
_histETHighQb.resize(5);
for (size_t ix = 0; ix < 3; ++ix) {
book(_histETHighQb[ix], 30 + ix, 1, 1);
book(_weightETHighQb[ix], "TMP/ETHighQb" + to_string(ix));
}
// Histograms for the averages
book(_histAverETCentral, 33, 1, 1);
book(_histAverETFrag, 34, 1, 1);
}
/// Analyze each event
void analyze(const Event& event) {
// DIS kinematics
const DISKinematics& dk = apply<DISKinematics>(event, "Kinematics");
if (dk.failed()) vetoEvent;
double q2 = dk.Q2();
double x = dk.x();
double y = dk.y();
double w2 = dk.W2();
// Kinematics of the scattered lepton
const DISLepton& dl = apply<DISLepton>(event, "Lepton");
if (dl.failed()) vetoEvent;
const FourMomentum leptonMom = dl.out();
const double enel = leptonMom.E();
const double thel = 180 - leptonMom.angle(dl.in().mom()) / degree;
// Extract the particles other than the lepton
Particles particles = apply<FinalState>(event, "FS").particles();
// Cut on the forward energy
double efwd = 0.;
for (const Particle& p : particles) {
const double th = 180 - p.angle(dl.in()) / degree;
if (inRange(th, 4.4, 15.0)) efwd += p.E();
}
// There are four possible selections for events
bool evcut[4];
// Low Q2 selection a
evcut[0] = enel / GeV > 12. && w2 >= 4400. * GeV2 && efwd / GeV > 0.5 && inRange(thel, 157., 176.);
// Low Q2 selection b
evcut[1] = enel / GeV > 12. && inRange(y, 0.3, 0.5);
// High Q2 selection a
evcut[2] = inRange(thel, 12., 150.) && inRange(y, 0.05, 0.6) && w2 >= 4400. * GeV2 && efwd > 0.5;
// High Q2 selection b
evcut[3] = inRange(thel, 12., 150.) && inRange(y, 0.05, 0.6)
&& inRange(w2, 27110. * GeV2, 45182. * GeV2);
// Veto if fails all cuts
/// @todo Can we use all()?
if (!(evcut[0] || evcut[1] || evcut[2] || evcut[3])) vetoEvent;
// Find the bins
int bin[4] = {-1, -1, -1, -1};
// For the low Q2 selection a)
if (q2 > 2.5 * GeV2 && q2 <= 5. * GeV2) {
if (x > 0.00005 && x <= 0.0001) bin[0] = 0;
if (x > 0.0001 && x <= 0.0002) bin[0] = 1;
if (x > 0.0002 && x <= 0.00035) bin[0] = 2;
if (x > 0.00035 && x <= 0.0010) bin[0] = 3;
}
else if (q2 > 5. * GeV2 && q2 <= 10. * GeV2) {
if (x > 0.0001 && x <= 0.0002) bin[0] = 4;
if (x > 0.0002 && x <= 0.00035) bin[0] = 5;
if (x > 0.00035 && x <= 0.0007) bin[0] = 6;
if (x > 0.0007 && x <= 0.0020) bin[0] = 7;
}
else if (q2 > 10. * GeV2 && q2 <= 20. * GeV2) {
if (x > 0.0002 && x <= 0.0005) bin[0] = 8;
if (x > 0.0005 && x <= 0.0008) bin[0] = 9;
if (x > 0.0008 && x <= 0.0015) bin[0] = 10;
if (x > 0.0015 && x <= 0.040) bin[0] = 11;
}
else if (q2 > 20. * GeV2 && q2 <= 50. * GeV2) {
if (x > 0.0005 && x <= 0.0014) bin[0] = 12;
if (x > 0.0014 && x <= 0.0030) bin[0] = 13;
if (x > 0.0030 && x <= 0.0100) bin[0] = 14;
}
else if (q2 > 50. * GeV2 && q2 <= 100. * GeV2) {
if (x > 0.0008 && x <= 0.0030) bin[0] = 15;
if (x > 0.0030 && x <= 0.0200) bin[0] = 16;
}
// check in one of the bins
evcut[0] &= bin[0] >= 0;
// For the low Q2 selection b)
if (q2 > 2.5 * GeV2 && q2 <= 5. * GeV2) bin[1] = 0;
if (q2 > 5. * GeV2 && q2 <= 10. * GeV2) bin[1] = 1;
if (q2 > 10. * GeV2 && q2 <= 20. * GeV2) bin[1] = 2;
if (q2 > 20. * GeV2 && q2 <= 50. * GeV2) bin[1] = 3;
if (q2 > 50. * GeV2 && q2 <= 100. * GeV2) bin[1] = 4;
// check in one of the bins
evcut[1] &= bin[1] >= 0;
// for the high Q2 selection a)
if (q2 > 100. * GeV2 && q2 <= 400. * GeV2) {
if (x > 0.00251 && x <= 0.00631) bin[2] = 0;
if (x > 0.00631 && x <= 0.0158) bin[2] = 1;
if (x > 0.0158 && x <= 0.0398) bin[2] = 2;
}
else if (q2 > 400. * GeV2 && q2 <= 1100. * GeV2) {
if (x > 0.00631 && x <= 0.0158) bin[2] = 3;
if (x > 0.0158 && x <= 0.0398) bin[2] = 4;
if (x > 0.0398 && x <= 1.) bin[2] = 5;
}
else if (q2 > 1100. * GeV2 && q2 <= 100000. * GeV2) {
if (x > 0. && x <= 1.) bin[2] = 6;
}
// check in one of the bins
evcut[2] &= bin[2] >= 0;
// for the high Q2 selection b)
if (q2 > 100. * GeV2 && q2 <= 220. * GeV2)
bin[3] = 0;
else if (q2 > 220. * GeV2 && q2 <= 400. * GeV2)
bin[3] = 1;
else if (q2 > 400.)
bin[3] = 2;
// check in one of*GeV the bins
evcut[3] &= bin[3] >= 0;
// Veto if fails all cuts after bin selection
/// @todo Can we use all()?
if (!(evcut[0] || evcut[1] || evcut[2] || evcut[3])) vetoEvent;
// Increment the count for normalisation
if (evcut[0]) _weightETLowQa[bin[0]]->fill();
if (evcut[1]) _weightETLowQb[bin[1]]->fill();
if (evcut[2]) _weightETHighQa[bin[2]]->fill();
if (evcut[3]) _weightETHighQb[bin[3]]->fill();
// Boost to hadronic CoM
const LorentzTransform hcmboost = dk.boostHCM();
// Loop over the particles
double etcent = 0;
double etfrag = 0;
for (const Particle& p : particles) {
// Boost momentum to CMS
const FourMomentum hcmMom = hcmboost.transform(p.momentum());
double et = fabs(hcmMom.Et());
double eta = hcmMom.eta();
// Averages in central and forward region
if (fabs(eta) < 0.5) etcent += et;
if (eta > 2 && eta <= 3.) etfrag += et;
// Histograms of Et flow
if (evcut[0]) _histETLowQa[bin[0]]->fill(eta, et);
if (evcut[1]) _histETLowQb[bin[1]]->fill(eta, et);
if (evcut[2]) _histETHighQa[bin[2]]->fill(eta, et);
if (evcut[3]) _histETHighQb[bin[3]]->fill(eta, et);
}
// Fill histograms for the average quantities
if (evcut[1] || evcut[3]) {
_histAverETCentral->fill(q2, etcent);
_histAverETFrag->fill(q2, etfrag);
}
}
// Finalize
void finalize() {
// Normalization of the Et distributions to unit cross-section
// These histograms are filled once per particles though,
// so no unit area to be expected
/// @todo Simplify by using normalize() instead? Are all these being normalized to area=1?
for (size_t ix = 0; ix < _weightETLowQa.size(); ++ix) {
if (_weightETLowQa[ix]->val()) scale(_histETLowQa[ix], 1 / *_weightETLowQa[ix]);
}
for (size_t ix = 0; ix < _weightETHighQa.size(); ++ix) {
if (_weightETHighQa[ix]->val()) scale(_histETHighQa[ix], 1 / *_weightETHighQa[ix]);
}
for (size_t ix = 0; ix < _weightETLowQb.size(); ++ix) {
if (_weightETLowQb[ix]->val()) scale(_histETLowQb[ix], 1 / *_weightETLowQb[ix]);
}
for (size_t ix = 0; ix < _weightETHighQb.size(); ++ix) {
if (_weightETHighQb[ix]->val()) scale(_histETHighQb[ix], 1 / *_weightETHighQb[ix]);
}
}
/// @}
private:
/// @name Histograms
/// @{
vector<Histo1DPtr> _histETLowQa;
vector<Histo1DPtr> _histETHighQa;
vector<Histo1DPtr> _histETLowQb;
vector<Histo1DPtr> _histETHighQb;
Profile1DPtr _histAverETCentral;
Profile1DPtr _histAverETFrag;
/// @}
/// @name Storage of weights for normalisation
/// @{
array<CounterPtr, 17> _weightETLowQa;
array<CounterPtr, 7> _weightETHighQa;
array<CounterPtr, 5> _weightETLowQb;
array<CounterPtr, 3> _weightETHighQb;
/// @}
};
RIVET_DECLARE_ALIASED_PLUGIN(H1_2000_I503947, H1_2000_S4129130);
}
Aliases: - H1_2000_S4129130